Molten Salt-Directed Catalytic Synthesis of 2D Layered Transition-Metal Nitrides for Efficient Hydrogen Evolution

Abstract

Facile synthesis of single-crystal 2D layered transition-metal nitrides (TMNs) is of crucial importance for the development of forthcoming technologies, such as superconducting, electromagnetic interference shielding, and energy-related applications. However, the fabrication of TMNs with natural 2D layered structure is thermodynamically difficult, in which stringent synthesis constraints have limited the exploration of this important class of functional materials. Here, we employed alkali molten salts as catalysts to achieve facile and large-scale (over decagram) synthesis of a family of 2D layered TMNs, such as MoN 1.2 , WN 1.5 , and Mo 0.7 W 0.3 N 1.2 , under atmospheric pressure. Ex-situ experiments reveal that the molten salt can lower the formation energy of 2D layered TMNs by assuring a liquid-gas synthesis and forming a TMN-salt-TMN superstructure as an intermediate. The resultant 2D layered TMNs show superior performance in hydrogen evolution reaction, demonstrating the immense potential of 2D layered TMNs for energy-related applications and beyond.

Stable and Highly Efficient Hydrogen Evolution from Seawater Enabled by an Unsaturated Nickel Surface Nitride

“…[ 21,22 ] Consequently, material optimization strategies, such as vacancy engineering, alloying, interface engineering, and heteroatom doping are usually needed to improve their activity. [ 23–28 ] For example, interfacing MoN with C 3 N 4 can greatly promote HER activity in alkaline media. [ 29 ] Tungsten and phosphorus doping in Co 3 N can manipulate the dehydrogenation kinetics and increase hydrogen production.…”

“…Using this strategy, the N atom ratio in the metal matrix can be tuned to regulate the TMN electronic structure. [ 18,24,25,30 ] The two main approaches to controlling the nitrogen content in TMNs are the nitrogen‐rich process and the incomplete nitridation process. [ 31–33 ] The nitrogen‐rich process aims to embed extra nitrogen atoms into the TMN lattice but usually requires high‐temperature and high‐pressure conditions due to sluggish thermodynamics.…”

Phase‐Separated Mo–Ni Alloy for Hydrogen Oxidation and Evolution Reactions with High Activity and Enhanced Stability

“…[ 1–5 ] The advantage of alkaline polymer electrolyte fuel cells (APEFCs) and alkaline water electrolysis (AWE) is the use of nonprecious metal catalysts, which is expected to significantly reduce the cost and promote the practical application of hydrogen energy. [ 6–8 ] At present, major obstacles to the application of APEFC and AWE are the slow kinetics of hydrogen electrode reactions and oxygen electrode reactions. [ 9,10 ] Hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) belong to hydrogen electrode reactions, and Mo–Ni alloy is one of the most promising electrocatalysts for hydrogen electrode reactions.…”

Two‐Dimensional Porous Molybdenum Phosphide/Nitride Heterojunction Nanosheets for pH‐Universal Hydrogen Evolution Reaction

“…In this regard, two‐dimensional (2D) materials are promising catalysts owning to their unique structure favorable to exposure of more accessible surface [25–29] . For example, the 2D molybdenum nitrite shows obvious activity for HER with η 10 =129 mV [30] . Furthermore, the formation of pores can enhance mass‐transfer ability, thus benefiting the improvement of the performance [31–33] .…”